1. Field of the Invention
The present invention relates to an apparatus for removing sediment, sludge, liquid, etc. from the bottom of a settling basin or tank, and more particularly relates to a drive mechanism for propelling a sludge suction manifold along the bottom surface of the settling basin for withdrawing sediment and sludge from the basin, for instance, water from an oil/water settling basin, or generally any application wherein collected solids or liquid is to be withdrawn from the bottom of a settling basin or tank.
2. Description of the Prior Art
Clarifiers and settling basins for water- and other liquid-treatment plants are designed to collect sediment and sludge on the bottom thereof, thereby permitting the clarified effluent to be taken from the top of the basin and reused, recycled, or further treated. Sediment and sludge that separate from the liquid collect on the bottom of the settling basin, and periodically must be removed in order to prevent thick accumulations of sludge and sediment in the basin. Frequently, the sludge-containing liquid includes caustic or petroleum-based contaminants that would interfere with the efficient operation of submerged electric motors used either to pump sediment and sludge from the settling basin bottom, or to propel a sludge suction nozzle or manifold along the bottom of the settling basin. Therefore, currently used devices incorporate pneumatically actuated pumping and sludge suction manifold propelling mechanisms.
Various devices are in current use for removing such sludge and sediment. Typically, as shown in U.S. Pat. No. 4,401,576, a sludge collection or suction manifold is attached to a collection body that travels along a track fixed to the bottom of the settling basin. Propulsion systems for such sludge collection manifolds typically utilize a pair of clamps that alternately clamp onto the track along the bottom of the settling basin in a specified sequence such that (1) a leading clamp clamps onto the track, (2) a trailing clamp is shifted forward toward the leading clamp, (3) the trailing clamp clamps onto the track and the leading clamp is released from the track, (4) the trailing clamp shifts to the back of the propulsion mechanism, thereby propelling the propulsion mechanism forwardly, (5) the leading clamp clamps onto the track and the trailing clamp releases from the track, and (6) the sequence repeats itself so as to incrementally propel the propulsion mechanism and sludge collection manifold along the track. Similar systems, such as that shown in U.S. Pat. No. 5,078,873 also incorporate the clamp, slide, clamp, release, propel, clamp, release, slide sequence of incrementally moving the suction manifold (suction housing) along the bottom of the settling basin for removing the collected sludge and sediment therefrom.
Other sludge removal systems, as shown in U.S. Pat. No. 5,219,470, utilize a rotating suction housing in the bottom of a cylindrical basin that simply rotates about its center along the bottom of a circular basin for sediment and sludge removal.
Still other devices, as shown in U.S. Pat. Nos. 5,037,486 and 1,918,742, utilize externally-controlled and propelled mechanisms for moving the suction manifolds along the bottoms of the settling basins.
Problems with these currently used devices are that the externally- or remotely-controlled propulsion mechanisms for the sludge suction manifolds are much more complicated and have many more moving parts than the pneumatically actuated submerged propulsion systems. Therefore, these externally- or remotely-controlled propulsion mechanisms are much more prone to problems and failure. The pneumatically actuated propulsion systems that incrementally or step-wise pull the sludge suction housing along the bottom of the settling basin using the clamp, pull, unclamp, slide, etc. sequence must follow a straight track in the bottom of the settling basin, and therefore, are limited to only forward and reverse movement in a straight line.
In addition, because of the step-wise incremental movement of such systems, the "vacuuming" or "suction removal" of the sediment and sludge is not even or uniform, but rather is segmented. Specifically, as the clamps of the propulsion system are being shifted in order to clamp onto the track, the propulsion mechanism is actually stationary for a finite amount of time that the trailing clamp is being shifted to its forward position. In these series of stationary positions, the suction housing sucks more of the sediment and sludge from the settling basin bottom than it does when it is being propelled forward (i.e., when it is moving). This stop-start-stop-start movement of the propulsion system results in uneven sediment removal, and specifically results in rows of sludge and sediment being left on the bottom surface of the settling basin between the locations where the propulsion mechanism has stopped in order to shift the trailing clamp for the subsequent incremental "pull". If the sequence and speed of the propulsion system are slowed sufficiently to permit efficient and uniform removal of sediment and sludge from the settling basin bottom, the incremental times that the clamps are repositioning themselves for the subsequent "pull", the vacuum/suction mechanism withdraws a large amount of effluent unnecessarily from the settling basin, the sediment and sludge directly under the temporarily stationary suction housing having been already withdrawn from the basin bottom during the slow step-wise progression and stationary positioning of the suction housing during the slowed propulsion cycle.